Treatment of tobacco to reduce polyphenol content

ABSTRACT

The polyphenol content of tobacco is reduced with minimal effect F. the desired characteristics of the final tobacco which has been moistened by contact with water or water vapor so that the moisture content of the said tobacco is at least 70 percent and is product by subjecting tobacco which has been moistened by contact with water or water vapor so that the moisture content of the said tobacco is at least 70 percent and is in the yellowed state to a short term of heating between about 140* and about 180* F. to initiate oxidative browning and thereafter holding the tobacco at a temperature between about 70* and about 110* F. until a major portion of the polyphenol content thereof is enzymatically oxidized. The heating may be effected by infrared radiation or by contacting the tobacco with hot gases or hot water. The tobacco may be treated either in whole leaf or in shredded form.

United States Patent Inventor Appl. No.

Filed Patented Assignee William H. Johnson Raleigh, N.C. 808,146

Mar. 18, 1969 Aug. 17, 1971 Research Corporation New York, N.Y.

TREATMENT OF TOBACCO TO REDUCE OTHER REFERENCES Bulk Curing Of BrightLeaf Tobacco (pub.) Johnson,

Henson, Hassler & Watkins from Tobacco Science Mar. 1960 p. 22- 28 inc.

Primary Examiner-Melvin D. Rein Attorney-Stowe and Stowell ABSTRACT: Thepolyphenol content of tobacco is reduced with minimal effect F. thedesired characteristics of the final tobacco which has been moistened bycontact with water or water vapor so that the moisture content of thesaid tobacco is at least percent and is product by subjecting tobaccowhich has been moistened by contact with water or water vapor so thatthe moisture content of the said tobacco is at least 70 percent and isin the yellowed state to a short term of heating between about and aboutF. to initiate oxidative browning and thereafter holding the tobacco ata temperature between about 70 and about 1 10 F. until a major portionof the polyphenol content thereof is enzymatically oxidized. The heatingmay be effected by infrared radiation or by contacting the tobacco withhot gases or hot water. The tobacco may be treated either in whole leafor in shredded form. v

YELLOWED TOBACCO LEAVES TURGOR I counmomns I ii irttttig TY 3 THERMALlNITIATlON 0F POLYPHENOL OXIDATION )4 LOW TEMPERATURE POLYPHENOLOXIDATION RECONDITIONING PATENTEU AUGI H9?! 3,599,645

SHEET 1 BF 2 I YELLOWED TOBACCO LEAVES @imj TURGOR CONDITIONING Ll lfifiij THERMAL INITIATION OF POLYPHENOL OXIDATION [EB Emi I/f4 LOWTEMPERATURE POLYPHENOL OXIDATION I S H R E DDINO L 1 DRYING JBEPQ IQ 6RECONDITIONING mvsmon I WILLIAM H. JOHNSON BY M d fwefl ATTORNEYfiPATENTEDAHGIIIS?! 3 599 5 5 sum 2 OF 2 g. a a. 2 a

I I l J 5 IO I5 20 25 TIME (SECONDS) FIG. 2

INVENTOR FIG. 3 WILLIAM H. JOHNSON BY M ATTOR NEYK TREATMENT OF TOBACCOTo REDUCE POLYPHENOL CONTENT The invention relates to a method wherebythe polyphenol compound content of tobacco may be substantially reduced.

Recent investigations have indicated that certain polyphenol compoundssuch as chlorogenic acid, present in tobacco, are precursors of phenols.in tobacco smoke, particularly cigarette smoke, and a principal objectof the invention is the provision of a method whereby such compoundsmaybe substantially reduced in amount with minimal effects on the desiredcharacteristics of the final tobacco product.

The total phenol content of tobacco has been identified as an importantcontributor to tumorigenic activity of smoke condensate or to ciliatoxicity of tobacco smoke. Reference is made specifically to the book,Tobacco and Tobacco Smoke,. Academic Press, New York, 1967, by E. L.Wynder and E. Hofiman who give a rather complete account of work in thearea of experimental tobacco carcinogenesis. Numerous tests havedemonstrated tumor promoting activity for the phenolic fraction of smokecondensate whenapplied in skin tests on mice. Furthermore, thetumorigenic activity has been 'found higher for tobacco smoke condensatehaving higher 'levels of phenols.

In other studies, 1 percent concentrations of phenol were toxic to clamgill cilia; while 0.05 percent concentration induced total stasis,without recovery within a -minute observation period. The cilia, finehairlike structures on the inner linings of the throat and lungs, playan important role in mucus transport and in the cleansing action of thelungs by propelling foreign matter back to the mouth where it can beexpelled.

It, therefore, appears to be highly desirable in the interest ofproducing less hazardous cigarettes and other tobacco products that thephenolic content of tobacco smoke be reduced. Polyphenols, such aschlorogenic acid, present in tobacco have been identified as specificprecursors of phenols and occur to levels of 6 to 7 percent of totalweight. The present invention provides a method whereby polyphenolcompounds may be systematically reduced by amounts up to 85 percent ofthat originally present.

' The object of the invention is accomplished by subjecting tobacco inthe yellowed state during curing to a short term of heating at atemperature between about 140 and about 180 F. to initiate oxidativebrowning and thereafter holding the tobacco at a temperature betweenabout 70 and about 1 10 F. until a major portion of the polyphenolcontent thereof is enzymatically oxidized.

The invention will be more particularly described with reference to theaccompanying drawings in which:

FIG. 1 is a generalized flow sheet of the method of the invention;

FIG. 2 is a graph of the oxidative browning initiating heat treatment ofthe invention; and

I FIG. 3 is a diagrammatic representation of an illustrative form ofapparatus suitable for carrying out the oxidative browning initiatingheat treatment of the invention.

Typically the tobacco, after harvest, is yellowed (1, FIG. 1) undercontrolled temperature and humidity conditions, for example at 85 tol05F. at 85 to 95 percent relative humidity during a period of about 24 to72 hours, depending on maturity, leaf position on the stalk and thelike. At the end of this step, major chemical reactions of the curingprocess have occurred such as starch hydrolysis, proteolysis andchlorophyll oxidation, and the leaf has a yellow color.

The yellow leaf is then turgor conditioned (2, FIG. 1) to a moisturecontent of 70 to 85 percent (wet basis) by passin'g air at a relativelyhumidity of 95-100 percent over the whole or the shredded leaf or byimmersing the tobacco in water. The latter is particularly effective andrapid if the tobacco is in the shredded state and requires no more than3--5 hours.

The conditioned tobacco is then rapidly heated (3', FIG. 1). to atemperature in the range from about 140 to about 180 F.

and for about 5 to 20 seconds,.as shown in FIG; 2, the time of heatingbeing longer at the lower temperatures. In the illustrative exampleshown in FIG. 2, the tobacco is heated to 180 F. in about 15 seconds andheld at l 80 for about 5 seconds when it is rapidly cooled to about 75F..At 160 F. the time at temperature should be about 10 seconds; whileat 140 F., 15 to 20 seconds at temperature is desirable. ln 'gene'ralfbptimal results are obtained by the shorter time of heating in theneighborhood of 180 F. J j

The tobacco is then quickly cooled to a temperature in the range fromabout 70 to about 110 F. where it is held for about 30 minutes (4,FIG. 1) for substantial completion (up to 85 percent or more) of thepolyphenol oxidation reactions.

The thermal treatment for initiation of polyphenol oxidation can beeffected by passing hot air through or over the tobacco, by irradiatingthetobacco with infrared heat or by immersing the tobacco in hot water.v

Treatment with hot water is particularly effective in obtaining rapidand closely controllable heat treatment. A suitable heating apparatus isshown in FIG. 3 wherein an immersion tank 10 is provided with a hotwater inlet 11 and outlet 12.

The tobacco 13 to be treated, in whole leaf or shredded form, is passedthrough the body of water in the tank at the desired rate by means ofconveyor 14 in cooperation with hold down flight 15. The tobacco leavingthe tank is quickly cooled to the temperature for carrying out thepolyphenol oxidation reactions by the evaporative cooling action of astream of air from conduit 16.

Following the polyphenol oxidation step, the tobacco is dried (5,FIG. 1) by heated air circulated on, over or through the tobacco or byfreeze-drying the tobacco by the methods described in my applicationSer. No. 707,064, filed Feb. 21, 1968. Following drying, the tobacco isreconditioned (6, FIG. 1) to safe handling moisture levels of about12-20 percent (wet basis), for example, with humidified air at 70 F. Asindicated in FIG. 1, shredding of the leaf tobacco may be carried outbefore or after any stage in the treating process.

Early shredding tends to facilitate handling and improve uniformity.

In the foregoing illustrative discussion of the method, conditions aredescribed for achieving maximum reduction in polyphenol content underoptimum conditions, with minimal effect on the desired characteristicsof the tobacco product. First, the tobacco following harvest undergoesimportant biochemical transformations of the coloring phase of curing toachieve desired levels of sugars, breakdown of complex proteins, etc.This is important in achieving desirable flavor and smokecharacteristics in the tobacco. Turgor conditioning, next, establisheshigh moisture levels for assuring an optimal oxidative reaction; sincethe biochemical reaction requires an aqueous state. This is followed bya rapid thermal treatment which elevates the tobacco temperature withinseconds to about 140 to about 180 F. for a short term of heating toinitiate oxidative browning.

Oxidation of polyphenols, and particularly odiphenols, is associated oroccurs simultaneously with oxidative browning, which is initiated atelevated temperatures. There is indication that the oxidation product ofpolyphenol oxidation contains protein and iron to give a high molecularweight compound. At leaf temperatures above l35l40 F. denaturation andprotoplasmic coagulation occur rapidly. It is considered that structuralmodifications occur in cytoplasmic membranes at these temperatures whichpermit commingling of oxidative enzymes, substrates and oxygen withinthe cell. This irreversible change in cytoplasmic membranes allows freerand more rapid movement of reactants for oxidative browning, includingpolyphenol oxidation.

Laboratory studies were conducted to determine the temperature range formost effectively initiating polyphenol oxidation. The temperature-timetreatments as discussed were found to be optimal. Below F., the testsindicated less extensive modification in cytoplasmic membranes, basedonelectrical conductivity and moisture permeability observations,'to givenoticeably slower and less-extensive oxidative browning. ABove l80 F.,the reaction was triggered; howreduce or tivation effects are notsignificant. Colorimetric observations have indicated that in mostleaves complete oxidative browningis efi'ected within 5 to 25 minutes.For complete reaction in at least 95 percent of the tobacco, about 30minutes should be provided.

Treatment, of tobacco varieties, Golden Wilt, Yellow Special A and Coker239,by the method of the invention wherein the leaf tobacco was heatedin 20 seconds to about 180 F. as in FIG. 2 to initiatepolyphenoloxidation and then allowed to brown at about 75 F. for 30 minutesresulted in uniform elimination of about 85 percent of the polyphenolcontent-of the tobacco expressed as chlorogenic acid.

I claim:

l. A method of curing tobacco which comprises bringing tobacco in theyellowed state to a moisture content of at least 70 percent bycontacting'the tobacco with a material consisting of water or watervapor, subjecting the thereby turgor conditioned tobacco to atemperature of from about 140 to about l80 F. for from about 5 to about20 seconds to initiate oxidative browning with concurrent polyphenoloxidation and thereafter holding the tobacco at a temperature of fromabout to about'l 10 F. for from about 5 to about 30 minutes.

2. A method of curing tobacco as defined in claim 1 wherein the yellowedtobacco is shredded before it is subjected to the oxidative browninginitiatingheat treatment. 1

3. A method of curing tobacco as defined in 'claim 1 'wherein thetobacco is shredded afterit has been subjected to the oxidative browninginitiating heat treatment.

4. A method of curing tobacco as defined in claim 1 wherein the yellowedtobacco is heated to oxidative browning initiat-,

ing temperature by immersion in hot water.

5. A method of curing tobacco as defined in claim 1 wherein the yellowedtobacco is heated to oxidative browning initiating temperature bypassinghot air through or over the tobacco.

6. A method of curing tobacco as defined in claim 4 wherein the heatedtobacco is cooled to from about 70 to about 1 l0 F. by the evaporativecooling effect of a current of air.

7. A method as defined in claim 1 wherein the tobacco after oxidativebrowning is dried by low pressure sublimation of the water contentthereof from the frozen condition.

8. A method as defined in claim 1 wherein the tobacco after oxidativebrowning is dried by passing a current of air through or over thetobacco.

2. A method of curing tobacco as defined in claim 1 wherein the yellowedtobacco is shredded before it is subjected to the oxidative browninginitiating heat treatment.
 3. A method of curing tobacco as defined inclaim 1 wherein the tobacco is shredded after it has been subjected tothe oxidative browning initiating heat treatment.
 4. A method of curingtobacco as defined in claim 1 wherein the yellowed tobacco is heated tooxidative browning initiating temperature by immersion in hot water. 5.A method of curing tobacco as defined in claim 1 wherein the yellowedtobacco is heated to oxidative browning initiating temperature bypassing hot air through or over the tobacco.
 6. A method of curingtobacco as defined in claim 4 wherein the heated tobacco is cooled tofrom about 70* to about 110* F. by the evaporative cooling effect of acurrent of air.
 7. A method as defined in claim 1 wherein the tobaccoafter oxidative browning is dried by low pressure sublimation of thewater content thereof from the frozen condition.
 8. A method as definedin claim 1 wherein the tobacco after oxidative browning is dried bypassing a current of air through or over the tobacco.